Rice waste put to use in lithium batteries

It plays a massive role in feeding the world, and now rice can play a part in next-generation vehicles, according to new research from Korea.

For decades, researchers have tried to devise a use for vast amounts of waste from rice production, the husks, which comprise about 20 per cent of harvested rice kernels.

That's more than 80 million metric tons a year, given worldwide annual rice yield amounts to about 422 million metric tons.

Until now, practical uses of rice husks have been limited to a narrow range of low-value agricultural items such as fertiliser additives and bed soil because of their tough and abrasive properties.

But there's a big opportunity for further research targeting more valuable applications, researchers at Korean institutions including Chungnam National University believe, after they found silica in the husks can be converted to silicon and turned into anodes for high-capacity lithium batteries.

Silicon is in ever-increasing demand because the batteries are at the heart of electric and hybrid vehicles.

The silica on rice husks is unique as it is formed in layers that protect the inside of the kernel from bugs and bacteria, but are porous at the nano-scale level to allow air and water ventilation.

The researchers used several steps, including acid and heat treatments, to extract the silica.

And they found the extracted silicon had excellent electrochemical performance when used for the anodes.

The study was published in the Proceedings of the National Academy of Sciences journal.